Optical fiber and production method thereof

Abstract

An optical fiber, which has a zero-material dispersion wavelength equal to or greater than 2 μm, and a high nonlinear susceptibility χ 3 equal to or greater than 1×10 −12 esu, and uses tellurite glass having sufficient thermal stability for processing into a low loss fiber, employs a PCF structure or HF structure having strong confinement into a core region. This enables light to propagate at a low loss. The size and geometry of air holes formed in the core region, and the spacing between adjacent air holes make it possible to control the zero dispersion wavelength within an optical telecommunication window (1.2-1.7 μm), and to achieve large nonlinearity with a nonlinear coefficient γ equal to or greater than 500 W −1 km −1 .

1. An optical fiber composed of tellurite glass with a material zero-dispersion wavelength equal to or greater than 2 μm the optical fiber comprising:
 a core region; 
 a first cladding section that is formed in such a manner as to enclose said core region, and has a plurality of air holes in a circumferential direction of said core region and along an axial direction of said core region; and 
 a second cladding section that is formed in such a manner as to enclose said first cladding section, and has a refractive index approximately equal to an equivalent refractive index of said first cladding section; and 
 wherein a relative refractive-index difference between said core region and said first cladding section is equal to or greater than 2%, thereby controlling a zero dispersion wavelength at a 1.55 μm band which is an optical telecommunication window. 
 
     
     
       2. An optical fiber composed of tellurite glass with a material zero-dispersion wavelength equal to or greater than 2 μm and having a composition of TeO 2 —Bi 2 O 3 -LO-M 2 O—N 2 O 3 -O 2 O 5 , where
 L is at least one of Zn, Ba and Mg, 
 M is at least one alkaline element selected from Li, Na, K, Rb and Cs, 
 N is at least one of B, La, Ga, Al and Y, and 
 Q is at least one of P and Nb, and 
 components of said tellurite glass are 
 50<TeO 2 <90 (mol %), 
 1<Bi 2 O 3 <30 (mol %), and 
 1<LO+M 2 O+N 2 O 3 +Q 2 O 5 <50 (mol %), 
 wherein said optical fiber comprises: 
 a core region; 
 a first cladding section that is formed in such a manner as to enclose said core region, and has a plurality of air holes in a circumferential direction of said core region and along an axial direction of said core region; and 
 a second cladding section that is formed in such a manner as to enclose said first cladding section, and has a refractive index approximately equal to an equivalent refractive index of said first cladding section; and 
 wherein a relative refractive-index difference between said core region and said first cladding section is equal to or greater than 2%, thereby controlling a zero dispersion wavelength at a 1.55 μm band which is an optical telecommunication window. 
 
     
     
       3. An optical fiber composed of tellurite glass with a material zero-dispersion wavelength equal to or greater than 2 μm and having a composition of TeO 2 —Bi 2 O 3 -LO-M 2 O—N 2 O 3 -O 2 O 5 , where
 L is at least one of Zn, Ba and Mg, 
 M is at least one alkaline element selected from Li, Na, K, Rb and Cs, 
 N is at least one of B, La, Ga, Al and Y, and 
 Q is at least one of P and Nb, and 
 components of said tellurite glass are 
 50<TeO 2 <90 (mol %), 
 1<Bi 2 O 3 <30 (mol %), and 
 1<LO+M 2 O+N 2 O 3 +Q 2 O 5 <50 (mol %), 
 wherein said tellurite material glass is doped with at least one type of rare-earth ions selected from Ce 3+ , Pr 3+ , Nd 3+ , Pm 3+ , Sm 3+ , Eu 3+ , Tb 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+  and Yb 3+ , and 
 wherein said optical fiber comprises: 
 a core region; 
 a first cladding section that is formed in such a manner as to enclose said core region, and has a plurality of air holes in a circumferential direction of said core region and along an axial direction of said core region; and 
 a second cladding section that is formed in such a manner as to enclose said first cladding section, and has a refractive index approximately equal to an equivalent refractive index of said first cladding section; and 
 wherein a relative refractive-index difference between said core region and said first cladding section is equal to or greater than 2%, thereby controlling a zero dispersion wavelength at a 1.55 μm band which is an optical telecommunication window. 
 
     
     
       4. The optical fiber as claimed in  claim 1 , wherein said air holes of said first cladding section are formed at fixed intervals along the circumferential direction of said core region. 
     
     
       5. The optical fiber as claimed in  claim 2 , wherein said air holes of said first cladding section are formed at fixed intervals along the circumferential direction of said core region. 
     
     
       6. The optical fiber as claimed in  claim 3 , wherein said air holes of said first cladding section are formed at fixed intervals along the circumferential direction of said core region. 
     
     
       7. The optical fiber as claimed in  claim 1 , wherein said air holes of said first cladding section are formed in a multilayer fashion in a radial direction of said first cladding section. 
     
     
       8. The optical fiber as claimed in  claim 2 , wherein said air holes of said first cladding section are formed in a multilayer fashion in a radial direction of said first cladding section. 
     
     
       9. The optical fiber as claimed in  claim 3 , wherein said air holes of said first cladding section are formed in a multilayer fashion in a radial direction of said first cladding section. 
     
     
       10. The optical fiber as claimed in  claim 1 , wherein said air holes of said first cladding section are filled with a material having a refractive index lower than a refractive index of said second cladding section. 
     
     
       11. The optical fiber as claimed in  claim 2 , wherein said air holes of said first cladding section are filled with a material having a refractive index lower than a refractive index of said second cladding section. 
     
     
       12. The optical fiber as claimed in  claim 3 , wherein said air holes of said first cladding section are filled with a material having a refractive index lower than a refractive index of said second cladding section. 
     
     
       13. The optical fiber as claimed in  claim 1 , wherein said core region has a refractive index higher than a refractive index of a material of said first cladding section. 
     
     
       14. The optical fiber as claimed in  claim 2 , wherein said core region has a refractive index higher than a refractive index of a material of said first cladding section. 
     
     
       15. The optical fiber as claimed in  claim 3 , wherein said core region has a refractive index higher than a refractive index of a material of said first cladding section. 
     
     
       16. The optical fiber as claimed in  claim 1 , wherein a central section to become said core has tellurite glass, a refractive index of which differs from the refractive index of said tellurite glass, embedded in said central section. 
     
     
       17. The optical fiber as claimed in  claim 2 , wherein a central section to become said core has tellurite glass, a refractive index of which differs from the refractive index of said tellurite glass, embedded in said central section. 
     
     
       18. The optical fiber as claimed in  claim 3 , wherein a central section to become said core has tellurite glass, a refractive index of which differs from the refractive index of said tellurite glass, embedded in said central section.